1. Field of the Invention
The present invention relates to a heavy oil treating method and a heavy oil treating system. More particularly, the present invention relates to a method of contacting heavy oil with high-temperature, high-pressure water to remove metal components in the heavy oil, thereby obtaining light oil containing hydrocarbon gases, which is suitable as fuel for use in gas turbines, etc.
2. Description of the Related Art
In view of that heavy oil containing a large amount of heavy metals is not suitable as fuel for generation of electric power by gas turbines, methods of removing those heavy metals for conversion into a useful energy source are proposed in Patent Reference 1 (JP,A 2000-109850, Abstract) and Patent Reference 2 (JP,A 2003-49180, Abstract).
Patent Reference 1 discloses a method of contacting high-temperature, high-pressure water (supercritical water), an alkali and heavy oil with one another in a supercritical state (critical point of water: 374° C. and 22.1 MPa) to decompose the heavy oil, thereby producing light oil components, hydrocarbon gases, metal oxides, an alkaline salt, and supercritical water. The obtained decomposition product is separated by an extractor into the hydrocarbon gases, the light oil components, and water. By repeating those steps of modification and separation, metal components and sulfur in the heavy oil are removed and light oil is produced. The basis of that disclosed technique resides in reacting the heavy oil with the supercritical water under the presence of an alkali for conversion into the light oil.
However, adding an alkaline metal and others, as a modifying catalyst, in heavy oil is disadvantageous in that, when produced light oil is used as fuel for gas turbines, corrosion of gas turbine parts is caused unless the added alkaline metal and others are removed.
Patent Reference 2 discloses a method of contacting supercritical water and heavy oil with each other to dissolve light oil components in the supercritical water for separation into the light oil components and heavy oil components, and further contacting the remaining heavy oil components with the supercritical water for modification of the heavy oil components. The finally left residue is incinerated. To promote decomposition of the residue, Patent Reference 2 also discloses addition of an alkaline metal as a catalyst.
In any of the above-cited Patent References, the heavy oil components which have not dissolved in the supercritical water are further reformed, and an alkaline catalyst is added to decompose and modify those heavy oil components which are hard to modify. It is therefore problematic to employ the reformed light oil components, as they are, as fuel for gas turbines. Further, repeating the modifying step increases the fuel cost.